1.Field of the Invention
The present invention relates to a process for preparing polyurethane foams which are based on toluene diisocyanates. More specifically the present invention relates to a process wherein the isomer ratio of toluene diisocyanate is varied to impart to the resultant foams certain improvements in performance properties.
2. Summary of the Prior Art
The use of toluene diisocyanate in the preparation of flexible foams is generally known in the art. The following patents provide examples of the use of toluene diisocyanates in the preparation of polyurethane foams. See U.S. Pat. Nos. 2,929,802, 3,072,582, 3,325,823 and 4,246,356.
In the preparation of flexible foams, there are employed auxiliaries and additives, pertinent among which are blowing agents. The use of auxiliary blowing agents serves the purposes of controlling the foaming (exothermic) temperatures and controlling foam hardness. However, with the advent of relevant environmental regulations, the use of otherwise effective chloroflorocarbons as an auxiliary blowing agent is being curtailed or eliminated. As would be realized, the reduction in the use of the auxiliary blowing agents adversely affects foam hardness. Hence, much work is being done to find replacements for the chloroflorocarbon type auxiliary blowing agents.
The present invention provides a means for preparing flexible polyurethane foams with the desirable hardness with essentially no auxiliary blowing agents.